Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$134.25	13.447%	$152.3026	$152.30	$152.30	$152.30
Purchase #2	$225.67	8.787%	$245.4996	$245.50	$245.50	$245.50
Purchase #3	$36.42	3.672%	$37.7573	$37.76	$37.75	$37.80
Purchase #4	$18.76	4.503%	$19.6048	$19.60	$19.60	$19.60
Purchase #5	$234.94	3.676%	$243.5764	$243.58	$243.60	$243.60
Purchase #6	$115.67	6.798%	$123.5332	$123.53	$123.55	$123.50
Purchase #7	$34.56	11.399%	$38.4995	$38.50	$38.50	$38.50
7 purchase totals =	$800.27		$860.7734	$860.77	$860.80	$860.80